The invention concerns portable laser-projecting instruments useful particularly in construction layout, and more specifically with such an instrument producing at least four orthogonal output beams which can be of generally balanced intensity and preferably with all beams of uniform shape and originating from the same apparent point. The instrument may be self-leveling.
A variety of optical schemes have been disclosed for producing multiple output beams for a construction layout tool, from the beam of a single laser diode. U.S. Pat. Nos. 5,500,524, 5,617,202, 6,005,716, 6,154,319 and 6,327,090 show various arrangements for dividing a beam spatially into two, three, four or five beams, each output beam taking a portion of the cross section of the collimated laser diode beam, and some of these patents show combinations of such spatial beam division and the use of conventional beam splitters that reflect a desired portion of the light""s intensity and transmit the remainder. U.S. Pat. No. 5,144,487 describes a system for producing five output beams from a single collimated laser diode beam, using beam splitter optics.
In addition, a number of patents have shown the use of spatial beam division for laser or other light beams, for various purposes, most of which are unrelated to that of the present invention. See U.S. Pat. Nos. 543,730, 3,452,207, 3,663,890, 5,408,553, and German patents Nos. 2,738,348 and 3,502,382.
Beam splitter periscopes, generally of the type used in the invention, are known in binocular microscopes, to produce a binocular image from a single image. They have not been known in the context of laser tools.
Portable laser tools of the type generally contemplated in the present invention are useful particularly for layout purposes, especially construction layout. In one form, as in the present invention, these laser layout instruments have included a self-leveling feature, with an internal pendulum-like suspension for the laser and at least some of the optics. These have included true pendulums as in U.S. Pat. No. 5,144,487 and tilt compensation mechanisms as in U.S. Pat. No. 5,459,932. Thus, despite small tilt angles of the instrument""s housing when placed on sloped or uneven surfaces, such an instrument produces two, three, four or five orthogonal output beams, all substantially accurate level or plumb beams.
According to this invention, an instrument producing multiple laser output beams for layout purposes is designed to optimize desired beam intensity for the beams involved. The beam intensity for four or five output beams can be approximately equal or one or more beams can be produced with greater intensity for use at longer distances. In one embodiment, a laser instrument producing four output beams utilizes an oblong or elliptical beam cross section as produced by typical laser diodes even after collimation, and directs this oblong beam against a reflective element having three 45xc2x0-angled reflective facets. A beam-transmissive center portion of the reflective element, preferably a hole, is aligned between two opposed reflective facets, and a further reflective facet is included laterally to the side of the center hole. The oblong collimated beam preferably is centered on the central transmission hole, which takes up nearly the entire width of the beam""s cross section on the smaller axis. Two outer portions of the collimated beam, i.e., at the outer ends of the long axis, strike the two angled facets which are aligned with the center hole and produce two oppositely directed beams.
At the center hole or transmission area, where the beam""s intensity is greatest, not all of this beam region is allowed to pass through. A beam splitter periscope device is positioned before the center hole, diverting a preselected portion of the beam""s power in the center beam region, outwardly and then parallel to the collimated beam, then striking the other reflective facet to produce a side output beam. The power of the beam thus produced can be balanced with the power of the beam portion passing through the hole if desired, or intensity can be apportioned otherwise. In addition, the other two beams can be balanced against the transmitted beam and the periscope-produced beam, by adjusting the geometry of the reflective element.
To produce the cleanest output beams, similar in cross section and compact in size, masking may be employed for some or all beams. In one form the masking comprises circular apertures in a plate interposed in the path of the collimated beam, just before the beam reaches the reflective element.
In another embodiment five beams are produced using two beam splitter periscope devices in series in front of the reflective element. The geometry can be varied to collect more of the center beam region for purpose of dividing this region into three beams, if the five beams are to be generally balanced in intensity.
The system described preferably is included in a self-leveling laser projecting instrument, although other uses are possible. Such an instrument has the laser diode and optics pendulously suspended in a housing, either a true pendulum or tilt compensation arrangement as shown in U.S. Pat. No. 5,459,932. That patent and U.S. Pat. No. 5,144,487 are incorporated herein by reference regarding inclusion of the present optics in a self-leveling instrument.
It is thus among the objects of the invention to provide a laser layout instrument with multiple orthogonal output beams, preferably four or five, with optimal beam power (orthogonal as used herein means at 90xc2x0 or 180xc2x0 to one another). These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings.